Elderly man with stroke-like symptoms.

Our appreciation is extended to Dr. J. Nathan Smith, Indiana University Department of Radiology, for contributing this case.

Elderly man with stroke-like symptoms.

Elderly man with stroke-like symptoms.

Differential diagnosis:

• Acute infarct
• Dural venous sinus infarct
• Polycythemia/hemoconcentration

Actual diagnosis:  Hemoconcentration; Patient had documented hemoglobin of 16.9 GM/dl and hematocrit of 49.7%.

Elderly man with stroke-like symptoms.

There has been little discussion in the literature on the topic of polycythemia effects on non contrast enhanced CT of the head. Despite this, it has been documented that hemoconcentration can lead to hyperattenuation of cerebral vessels. The increase in attenuation results from the hemoglobin protein with a minimal contribution from increased iron content. Even with a normal hematocrit of 43%, intravascular blood may appear slightly hyperdense compared to surrounding brain tissue. At a hematocrit of 70%, the circulating blood appears 63% more dense. This can be confused with hyperdense artery sign, which would suggest acute infarct, and dural venous sinus thrombosis. The differentiating feature with hyperattenuation secondary to hemoconcentration is diffuse vascular involvement rather than involvement of a single artery in the case of acute thrombotic stroke. However, caution should be taken when evaluating cerebral imaging of patients with documented polycythemia since diffuse intravascular hyperdensity and dural venous sinus thrombosis may coexist in this population.

Polycythemia and hemoconcentration can produce hyperattenuation of cerebral arteries, veins, and venous sinuses. This appears as diffuse hyperattenuation of multiple vascular systems.

• Hemoconcentration and polycythemia can cause hyperattenuation of intravascular blood.
• This can mimic hyperdense artery sign and dural venous sinus thrombosis.
• Hyperattenuation in multiple vascular distributions suggests hemoconcentration.
• Care must be taken when evaluating imaging of patients with polycythemia as intravascular hyper density may coexist with dural venous sinus thrombosis. 

References: 

1. Gayathri, S., et al, Unique features of polycythemia observed on plain non contrast CT scan of head. Journal of Pediatric Neuroscience. 2010 Jan-Jun; 5(1): 27–29.
2. Healy, J.F. and Nichols, C., Polcythemia mimicking venous sinus thrombosis. American Journal of Neuroradiology. 2010 September; 23:1402-1403.

Elderly man with stroke-like symptoms.